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Title: Investigating the neutral sodium emissions observed at comets
Author: Birkett, K. S.
ISNI:       0000 0004 8498 8502
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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Neutral sodium emission is typically very easy to detect in comets, and has been seen to form a distinct neutral sodium tail at some comets. If the source of neutral cometary sodium could be determined, it would shed light on the composition of the comet, therefore allowing deeper understanding of the conditions present in the early solar system. Detection of neutral sodium emission at other solar system objects has also been used to infer chemical and physical processes that are difficult to measure directly. Neutral cometary sodium tails were first studied in depth at comet Hale-Bopp, but to date the source of neutral sodium in comets has not been determined. Many authors considered that orbital motion may be a significant factor in conclusively identifying the source of neutral sodium, so in this work details of the development of the first fully heliocentric distance and velocity dependent orbital model, known as COMPASS, are presented. COMPASS is then applied to a range of neutral sodium observations, including spectroscopic measurements at comet Hale-Bopp, wide field images of comet Hale-Bopp, and SOHO/LASCO observations of neutral sodium tails at near-Sun comets. The author finds that COMPASS is relatively successful at reproducing the morphology of the neutral sodium tails seen in wide field images, and to a lesser extent the intensity profiles produced by spectroscopic measurements. The success of COMPASS indicates that the current understanding of the physics of the production and evolution of neutral cometary sodium is broadly accurate. Using a simplistic dust tail source the author also finds that a source of neutral sodium within the dust tail is likely to result in a secondary neutral sodium tail feature, that has not yet been observed to the best of their knowledge.
Supervisor: Jones, G. H. ; Coates, A. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available